Technical Field
The present disclosure relates to an imaging optical system and an image capturing device. More particularly, the present disclosure relates to a compact imaging optical system and an image capturing device applicable to mobile terminals.
Description of Related Art
In recent years, with the popularity of mobile terminals having camera functionalities, the demand of miniaturized optical systems has been increasing. The sensor of a conventional optical system is typically a CCD (Charge-Coupled Device) or a CMOS (Complementary Metal-Oxide-Semiconductor) sensor. As the advanced semiconductor manufacturing technologies have allowed the pixel size of sensors to be reduced and compact optical systems have gradually evolved toward the field of higher megapixels, there is an increasing demand for compact optical systems featuring better image quality.
A conventional optical system employed in a portable electronic product mainly adopts a four-element lens structure. Due to the popularity of mobile terminals with high-end specifications, such as smart phones, tablet personal computers and wearable apparatus, the requirements for high resolution and image quality of present compact optical systems increase significantly. However, the conventional optical systems cannot satisfy these requirements of the compact optical systems.
Other conventional compact optical systems with five-element lens structure are also developed. However, it is unfavorable for arranging the lens elements, especially for the optical systems with large field of view, since the total track length is usually excessively long. Moreover, the difficulty of structure design for abutting and joining lens elements together is increased so as to intensify the tilt and decenter, which might lead to problems of worse image.